Stevenson S W, Dudley G A
Department of Kinesiology and Health Promotion, California State Polytechnic University, Pomona, CA 91768, USA.
Med Sci Sports Exerc. 2001 Aug;33(8):1304-10. doi: 10.1097/00005768-200108000-00010.
This study examined the influence of dietary creatine (CR) supplementation upon mechanical and hypertrophic responses to a well-defined conditioning stimulus provided by electromyostimulation (EMS).
Eighteen resistance-trained subjects were assigned CR or a placebo (PL) in a randomized, double-blind fashion. After CR loading (20 g x d(-1) for 7 d), CR supplementation (5 g x d(-1)) or PL was continued for 8 wk. During supplementation, EMS (3--5 sets of 10 coupled eccentric and concentric actions) was applied to the left m. quadriceps femoris (QF) twice weekly while subjects continued voluntary resistance training of both lower limbs unsupervised. Cross-sectional area (CSA) of each QF was assessed with magnetic resonance imaging (MRI). Torque during EMS was analyzed to assess muscle loading and fatigue resistance.
Maximal torque and the torque time integral increased markedly over training (P < or = 0.0001). These responses reflected activation of more muscle as EMS current was increased (about 16%), greater recovery between sets (P < or = 0.0423), and less fatigue during sets over training (P = 0.0002). CR did not influence these responses (P = 0.8093). In accord with these results, the increase in CSA for the stimulated QF (11%) was comparable for CR and PL (P = 0.2190). CSA in the nonstimulated QF increased 5% in CR (P = 0.0091) but did not change in PL.
We conclude that CR supplementation did not augment the mechanical or hypertrophic response to a precisely measured conditioning stimulus that attenuated but did not ameliorate fatigue. We suggest that enhanced fatigue resistance may not explain the apparent ergogenic effect of CR during voluntary training.
本研究探讨了膳食补充肌酸（CR）对电肌刺激（EMS）所提供的明确训练刺激的机械和肥大反应的影响。
18名经过抗阻训练的受试者以随机、双盲的方式被分配接受CR或安慰剂（PL）。在CR负荷期（20 g·d⁻¹，持续7天）后，继续补充CR（5 g·d⁻¹）或PL 8周。在补充期间，每周两次对左侧股四头肌（QF）进行EMS（3 - 5组，每组10次离心和向心联合动作），同时受试者在无监督的情况下继续进行双下肢的自主抗阻训练。用磁共振成像（MRI）评估每个QF的横截面积（CSA）。分析EMS期间的扭矩以评估肌肉负荷和抗疲劳能力。
在训练过程中，最大扭矩和扭矩时间积分显著增加（P≤0.0001）。这些反应反映出随着EMS电流增加（约16%），更多肌肉被激活，组间恢复更好（P≤0.0423），并且在训练过程中每组的疲劳程度更低（P = 0.0002）。CR对这些反应没有影响（P = 0.8093）。与这些结果一致，受刺激的QF的CSA增加（11%）在CR组和PL组中相当（P = 0.2190）。未受刺激的QF的CSA在CR组增加了5%（P = 0.0091），而在PL组没有变化。
我们得出结论，补充CR并没有增强对精确测量的训练刺激的机械或肥大反应，该训练刺激减轻但未改善疲劳。我们认为增强的抗疲劳能力可能无法解释CR在自主训练期间明显的促力作用。
